Electromagnetic device



April 18, 1933. B.` .1, BABBITT ELECTRMAGNETIC DEVICE Filed NOV. l0,1928 Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE BETHEL JAYBABBITT, OF RIVERSIDE, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY,INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK yELECTROMAGNETIC DEVICE Application tiled November 10, 1928. Serial No.318,323.

' This invention relates to electromagnetic devices, and moreparticularly to electromagnetic relays for use in signaling systems. Theprimary object of the invention is to '5 provide an electromagneticdevice of simple and durable construction having improved operatingcharacteristics.

One embodiment of the invention contemplates the provision of anelectromagnetic structure in which a frame having a core extending intoa magnetizing coil supports an armature with a core secured thereto eX-tending into the coil directly opposite the core of the frame. VThesecores are constructed and mounted to provide an air gap between them atthe center of the magnetizing coil so that upon energization of the coilthe magnetic flux which is of maximum density at the center of the coilwill produce powerful tractive forces across the air gap to actuate thearmature,

It is believed that a clear understanding of the invention may be had byreference to the following description, taken in con- 125 junction withthe accompanying drawing,

in which Fig. 1 is a plan View of an electromagnetic relay embodying theinvention;

Fig. 2 lis a side elevation thereof, and

Fig. 3 is a longitudinal sectional view taken on line 3 3 of Fig. 1.

Referring to the drawing wherein like numerals designate similar partsthroughout the various views, the4 numeral 10 designates a plate made ofmagnetic material, such as a suitable grade of soft iron, having an`upturned lug 11 for supporting one end of an armature 12 and providedwith threadi ed apertures 13-13vfor purposes of mount-` ing. As shown inFigs. 1 and 2, the armature is hinged to the lug 11 by means of a reedspring 14 of thin sheet steel secured to both the lug and the armature.The plate 1.0` and armature 12 are provided with right r angled portions17 and: 18 for limiting the downward movement of the armature and withsubstantially perpendicular tongues 15 and 16 separated by a small airgap and formed from partially severed parts of the 5 plate and armature,respectively.

Rigidly secured to the upper side of the plate 10 and the underside ofthe armature 1 2 and medially of the tongues 15-16 and right angledportions 17-1'8 are cores 22 and 21 made of magnetic material. To affordsufficient clearance between a magnetizing coil to be hereinafterdescribed and the movable core 21, the core 21 is made smaller than thecore 22. These cores are mounted directly opposite each other and areseparated by a minute air gap when the right angled portions 17-18 arein engagement with each other. The right angled portion 17 has securedthereto a threaded pin 23 extending through and beyond an aperture inthe right angled portion 18 and an adjustable stop nut 24 threaded onthe pin 23 limits the upward movement of the armature 12.

A hollow spool 30 having a plurality of turns of insulated wire 31 is soina-de that a forced fit is obtained on the lower stationary core 22secured onthe frame 10. This spool is usually made of phenol libre butit may be made of metalV such as the spools often made of copper whichare used for relays when the space available makes it impracticable formechanical strength reasons to employ phenol fibre. When metal spoolsare used a slot 32 is provided for preventing eddy currents. By mountingthe magnetizing coil on the lower core 22, the assembly is simplified sothat form wound coils can be used to reduce the cost of the relay. Ashas been previously explained, the core 21 of the armature 12 is madeslightly smaller than core 22 so that there will be suiiicient clearancebetween the spool 30 and the movable core 21 to permit the requiredmovement thereof in actuating the armature.' The ends of the wire 31forming the magnetizing Winding on the spool 30 are connected toterminals 33-34 which are insulatively mounted on the plate 10 by meansof screws 36-36 threaded therein, whereby the terminals can be readilyconnected to a source of electric-al energy to energize the winding.

In -addition to the terminals 33-34, contact springs 37-38 and 39-40separated by a' plurality of small insulators 42 are also mounted on theplate 1() byscrews 36-36. 100

, flux is of greatest density, creates a powerful These contact springsare provided at one end with a terminal porti-on 45 and at the other endwith a contact 46. Springs E37- 3S are disposed so as to be normally outof engagement and maintain their contacts 46 separated, whereas thesprings 39-40 are arranged toy normally press together and make contact.

The armature l2 has laterally extending arms 48-48 at its forward endwhich carry insulating pins 49 and 50. The insulating pin 49 engages thecontacting spring 37 and the insulating pin 50 protrudes through anopening in the spring 39 and engages the spring 40. The armature 12 isthus normally heldin engagement with a stop nut 24 by the resilience ofthe contacting springs 37 and 40 acting against the insulating pins49-50 carried by the armature 12.

1n operation, the terminals 33 and 34 are connected to a source ofelectrical energy (not shown) to energize the coil of wire 31 encirclingthe cores 21-22. An electric current traversing the turns of wire 31sets up a magnetic flux, which is of greatest density at the center ofthe magnetizing coil. The soft iron cores 21 and 22 in conjunction withthe parts 10, l2 and 15-18 afford a path of very low reluctance for theflux With the result that the cores become magnetized and the adjacentcore faces assume opposite polarity which result-s in mutual attractionbetween the stationary core 22 and the movable core 21. Since the coresare encircled by the magnctizing coil all of the flux passes through thecores to produce traction. The action of this flux in the air gapbetween the adjacent faces of the cores positioned midway between theends of the magnetizing coil where` the tractive effort in accordancewith Maxwells formula P=B2AK, in which B is the flux density, A is thearea of the core faces, and K is a proportionality constant, whence itis Seen the pull P is proportional to the square of the flux density inthe armature air gap.

Inasmuch as all of the flux traverses the cores, the flux density B is amaximum and a very effective pull is exerted whereby the core 21 and thearmature 12 are actuated to control any circuits connected to thecontacting springs 3?-38 and 39-40 through the movement of theinsulating blocks 4Q- 50 associated with the armature. Also, the rightangled portions 17 and 18 serve as a return path for the flux andprovide an auxiliary source of tract-ion in producing a tractive forceacross the air gap therebetween before the armature is actuated. Thetongues 15 and 1G are positioned close together before actuation of thearmature and provide a path of low reluctance to thus assist inproducing a greater tractive force by increasing the amount of effectiveflux. Upon actuation of the armature the tongue 16 moves at an anglerelative to the other tongue 1 5 and increases the distance therebetweento expedite the release of the armature when the energizing circuit isopened.

lVhen it is desired to restore the relay to its original condition, theenergizing circuit to theterminals 33-34 is opened. The current thenceases to flow in the magnetizing winding, the cores are demagnetized,and the armature is returned to its normal pos'p tion against the stopnut 24 by the resilience of the contacting springs 37 and 40.

The construction shown permits the use of a large number of contactingsprings for controlling a great number of clrcuits from one relay; formwound magnetizing coils can be used to facilitate manufacture andassembly and reduce the cost; and the positioning of the air gapmedially of the ends of the magnetizing coil reduces the leakage of theflux to a minimum and thus produces a very quick acting, heav dutyrelay, since all the magnetic flux is e ective in exerting tractiveeffort across the air gap within the magnetizing coil. Moreover, theplacing of the air gap at the center of the magnetizing coil reduces thepossibility of dirt and foreign material becoming lodged in the air gapand thus reducing the efliciency of the relay by obstructing the freemovement of the armature.

The above described type of structure is also particularly well adaptedto produce a relay having slightly retarded release characteristics byhaving the spool on which the coil is wound made of copper andeliminating the slot therein. For this type ofrelay,thetimeofreleaseoftliecontactingsprings throughout a wide range oftensions imposed thereon can be very accurately determined by specifyingthe size of the cores, the number of exciting ampere turns, and thesaturation value of the magnetic material of which the cores are made.

It will be understood that the invention herein described andillustrated is capable of many other modifications Without departingfrom the spirit and scope'of the invention.

What is claimed is:

1. In an electromagnetic device, a. coil arranged to be traversed by anelectric current for establishing an electromagnetic field, a magneticmember having a portion extending into the coil, a tongue fixed to themagnetic member, an armature hinged to the magnetic member and having aportion thereof extending into the magnetic field at the point of itsmaximum flux density, and a tongue fixed to the armature and cooperatingwith the tongues fixed to the magnetic member to provide between thearmature and the magnetic member an air gap and path of low reluctancewhich will be increased upon actuation of the armature.

2. In an electromagnetic device, a coil a1'- ranged to be traversed byan electric current for establishing an electromagnetic field, amagnetic member having a portion extending into the coil, a tongueformed on the magnetic member, an armature hinged to the magnetic memberand having a portion thereof extending into the magnetic iield at thepoint of its maximum flux density, a tongue formed on the armature andcooperating with the tongue formed on the magnetic member to providebetween the armature and the magnetic member an air gap and path of lowreluctance which will be increased upon actuation of the armature, andmeans for limiting the amount of movement of the armature outwardly andfor providing another air gap between the armature and the magneticmember.

3. A relay having a plurality of iiat spring contact members extendingsubstantially parallel to each other, an operating coil having its axistransversely arranged with respect to said contact members, and amagentic circuit including an armature moving in the axis of said coilfor operating said contact members, said magnetic circuit comprising anelongated extension for supporting said sprmgs.

4. A relay having a plurality of flat spring contact members extendingsubstantially parallel to each other, an operating coil having its axistransversely arranged with respect to said contact members, and amagnetic circuit including an armature moving in the axis of said coilfor operating said contact members, the axis of said coil being short ascompared with its average diameter, and the overall length of the relaybeing several times as great as the axis ofthe coil.

5. A relay having a plurality of flat spring contact members extendingsubstantially parallel to each other, an operating coil having its axistransversely arranged with respect to said contact members, and amagnetic circuit including an armature moving in the axis of said coilfor operating said contact members, said armature extending within thecoil to form a short air gap therein between itself and the adjacentportion of the magnetic circuit, and said springs being mounted on thestructure of said magnetic circuit at a point remote from said coil.

6. A relay comprising an elongated frame of magnetic material, anoperating coil within said frame near one end thereof and have ing itsaxis arranged transversely of said frame, a transverse support mountedon said frame near the opposite end thereof, a plurality of springcontact members mounted on the extremities of said support and extendingparallel with said frame on opposite sides of said coil, one side ofsaid frame being movable and carrying an armature in line with the axisof .said coil, and means carried by said movable side of the frame foractuating said springs.

In witness whereof, I hereunto subscribe my name this 29thday ofOctober, A. D., 1928.

BETHEL JAY BABBITT.

